The rear wheel suspension for a motor vehicle connects the architecture of the sprung vehicle mass to the architecture of the non-sprung and rotating rear wheels and associated tires, the rear tire-wheel assemblies. Furthermore, the rear wheel suspension controls the motion pattern of the rear tire-wheel assemblies with respect to the external impact from the road as well as to the internal impact from the propelling, braking and steering as initiated by the driver through the engine-transmission system, the braking system, the steering system and the rear and forward wheel suspensions.
The overall controllability in terms of steering, propelling and braking of the vehicle is closely related to the motion pattern of the four tire-wheel assemblies. The motions of the front tire-wheel assemblies are normally controlled by two independent front wheel suspensions while for the rear tire-wheel assemblies the rear wheel suspension as defined above controls the two rear tire-wheel assemblies by a multi-link beam suspension where the two suspension devices, one for each tire-wheel assembly, connect to each other through a transversal beam with special characteristics, where four longitudinal links, two on each side, connect the left and the right suspension devices to the vehicle body.
The front wheel suspensions and the rear wheel suspension together with the four tire-wheel assemblies constitute the un-sprung masses connected to the vehicle's sprung mass to which the driver is connected. During the vehicle's motion of combined forward running (surge), bounce, sway/veer, roll, pitch and yaw, these motion patterns and their time derivatives in all directions are guided such that a normal driver's capability of control enables the entire synthesized motion pattern of the vehicle to be fully controlled in a secure manner from the capability of the suspension to transform the superimposed useful control signals and disturbing noise, where the objectively measurable disturbing noise frequently overpowers the useful control signal, such that the noise signal is transformed into well defined perceived control signals in order to amplify useful control signals.
Vehicles are complex systems with human beings in the control loop. Although the dynamic behavior of vehicles in response to drivers' input may be simulated or measured, this understanding does not determine the issue of ‘good handling’ unless complemented with the understanding of how human beings work as control systems and how a driver's brain works in vehicle control.
It is therefore important to provide a system mechanization with a synthesized operation of the communication loop defined as “fail operate, fail operate, fail safe” normally used in safety critical systems such as Control Configured Vehicles (CCV). This requires a communication loop of quadruple redundancy and a dissimilar back up system, where the command media in our case is the entire vehicle-suspension architecture. The redundancy in the command media is here to be seen as flows of information of superimposed layers of power spectra where the driver's sensory system has capability to sense concurrently ongoing motion patterns in a similar way as our eye concurrently can perceive several colors or our ears concurrently can perceive several tones in music. The spectra as characterized by different frequencies should be in harmony with each other, i.e. redundant signals should be coherent.